Indexable cutting insert

Abstract

An indexable cutting insert (10) for a tool (18) adapted to cut internal right-angled corners in a work piece (19). The insert (10) has a square configuration and comprises a top major surface (11), a bottom major surface (12) and connecting side surfaces (13). The lines of junction between the top major surface and the side surfaces define the main cutting edges (14) and the minor cutting edges (15). The main cutting edges (14) transite into the second cutting edges (15) in the corners of the insert. Each second cutting edge (15D) projects from the square basical shape so that it will lift the inactive main cutting edge (14A) from the machined surface under the insert.

I claim: 
     
       1. An indexable cutting insert comprising upper and lower faces interconnected by four side surfaces, the intersection between said side surfaces and said upper face forming four main cutting edges each coinciding with an imaginary line; said imaginary lines intersecting to form a square, intersecting pairs of said imaginary lines defining four cutting corners; each said side surface including a projection disposed at one of said cutting corners whereby there are four said projections each disposed at one of said corners such that each projection is associated with two of said main cutting edges forming the respective corner; a first of such pair of main cutting edges being formed on said side surface carrying such projection, and a second of such pair of main cutting edges formed on the other side surface which forms such corner; each projection projecting transversely relative to its associated first main cutting edge and parallel to its associated second main cutting edge; each projection forming a minor cutting edge disposed outside of said square; each minor cutting edge being joined to and extending at an angle relative to its associated second main cutting edge; each minor cutting edge defining an active cutting edge when its associated first and second main cutting edges are inactive and active, respectively, so that said minor cutting edge maintains such inactive main cutting edge spaced from a workpiece being cut. 
     
     
       2. An indexable cutting insert according to claim 1, wherein said minor cutting edge is coplanar with said four main cutting edges. 
     
     
       3. An indexable cutting insert according to claim 2, wherein said lower face includes an outer periphery spaced inwardly relative to an outer periphery of said upper face, said upper face defining a chip surface for said main and minor cutting edges. 
     
     
       4. An indexable cutting insert according to claim 1, wherein each minor cutting edge is disposed at an acute angle relative to its associated first cutting edge. 
     
     
       5. An indexable cutting insert according to claim 1, wherein the length of each minor cutting edge is at least ten percent of each side of said square. 
     
     
       6. An indexable cutting insert comprising upper and lower faces interconnected by four side surfaces, the intersection between said side surfaces and said upper and lower faces forming four edges along said upper face and four edges along said lower face, each of said edges coinciding with an imaginary line, said four imaginary lines along said upper face intersecting to form an upper square and said four imaginary lines along said lower face intersecting to form a lower square of the same size as said upper square, two opposed ones of said edges of said upper face defining main cutting edges, and two opposed ones of said edges of said lower face defining main cutting edges which are offset by ninety degrees relative to said main cutting edges of said upper face, each of said main cutting edges of said upper face intersecting a non-cutting one of said edges of said upper face to form therewith a corner, each of said main cutting edges of said lower face intersecting a non-cutting one of said edges of said lower face to form therewith a corner, each said side surfaces including a projection disposed at one of said corners whereby there are four said projections each disposed at one of said corners such that two of said projections are associated with two of said corners of said upper edge and the other two of said projections being associated with two corners of said lower edge and being offset by ninety degrees relative to said two corners of said upper edge, each projection being formed on the side surface which carries said non-cutting edge associated with such projection; each projection projecting transversely relative to its associated non-cutting edge and parallel to its associated main cutting edge; each projection forming a minor cutting edge disposed outside of said square of its respective face; each minor cutting edge being joined to and extending at an angle relative to its associated main cutting edge; each minor cutting edge defining an active cutting edge when its associated main cutting edge is active, so that said minor cutting edge maintains its associated non-cutting edge spaced from a workpiece being cut. 
     
     
       7. An indexable cutting insert according to claim 6, wherein each said minor cutting edge is disposed outside of a plane defined by said square of its respective said face.